Backlights for transmissive spatial light modulators typically comprise an array of light sources and optical elements that typically use guiding and extraction of light to distribute light across the area of the spatial light modulator. The light sources may be provided for example by an array of LEDs on at least one side of a light guide plate.
Non-imaging backlights are typically arranged to direct the illumination from multiple light sources through a display panel into a substantially common viewing zone for each of the multiple light sources to achieve wide viewing angle and high display uniformity. Light source arrays for non-imaging backlights may be addressed with substantially the same input for all light sources. Light sources may further be arranged in strings to achieve compact electrical connection apparatus.
In contradistinction, directional backlights may be arranged to direct the illumination from multiple light sources through a display panel into respective different viewing zones, or windows, that are different for each of the multiple light sources, as generally discussed in U.S. patent application Ser. No. 13/300,293, entitled “Directional flat illuminators,” filed Nov. 18, 2011 and U.S. patent application Ser. No. 14/186,862, entitled “Directional backlight,” filed Feb. 21, 2014, both of which are herein incorporated by reference in their entireties. Directional backlights may achieve additional functionalities compared to non-imaging backlights including high efficiency modes of operation, privacy effect, high luminance for low power consumption and Lambertian operation for user comfort with extended display use. Further, in cooperation with fast update rate spatial light modulators autostereoscopic 3D and low off-axis contrast privacy modes of operation may be achieved.
The control of the mode of operation of directional backlights may be achieved through individual addressing of the light sources of the array of light sources in a manner that forms a desired viewing window structure. For example high efficiency operation may be achieved by addressing a small group of light sources whereas Lambertian operation may be achieved by addressing the whole array uniformly. Further, light may be directed towards an observer by adjusting illumination of light sources in response to measurement of their position.
The present disclosure achieves electrical contact to large arrays of independently light sources in a compact and low cost manner.